Method for producing textile yarn from a mono



Nov. 26, 1963 R. L. RUSH 3,112,150

METHOD FOR PRODUCING TEXTILE YARN FROM A MONOFILAMENT OF A BLEND OFOLEFIN POLYMERS Filed July 11, 1960 WIND-UP ROLL FIG. 3

F rs J 0 LL! U O O o II 7 J g co E E g INVENTOR. Jr- R. L. RUSH m o 8mwngw A 7' TOR/VEVS United States Patent Ofiiice 3,112,160 Patented Nov.26, 1963 METHOD FOR PRODUCING TEXTILE YARN FROM A MONOFILAB'IENT OF ABLEND F OLEFIN POLYMERS Robert L. Rush, Wellington, Kans., nssignor toPhiilips Petroleum Company, a corporation of Delaware Filed July 11,1960, Ser. No. 41,751 5 Claims. (CI. 18-54) This invention relates tothe manufacture of a multifibrous yarn from a continuous monofilament ofa blend of thermoplastic polymers. In another aspect it relates tocausing the fibrillation of a thermoplastic extrudate.

Thermoplastics have been considered, and certain types developed, as asource of textile fibers, but they have also been found to presentproblems which were long ago solved with the older cellulosic fibers.For example, the prior art teaches a method for fibrillation ofcontinuous, multifilament fibers, by cutting or abrasion, to provide ayarn with properties called for in many textile applications.

Polyolefins, among other thermoplasties, because of their chemicalresistivity are a class of textile yarns of highly desirable properties,if the physical processing requirements can be attained. Polyolefins canbe readily prepared as a continuous single filament by extrusion througha die. It is then desirable to form a multi-fibrous fiber therefrom inmany textile applications. However, when an attempt was made tofibrillate a monofilamcnt comprising a monopolyolefin, with a sharpedged means, as taught in the prior art, for multifilaments only,failure resulted. This failure came about because the monofilamenttended to be completely severed or abraidcd in two filaments by thecutting edge, rather than effecting a controlled fibrillation.

l have discovered that in order to fibrillate a monofilament of apolyolefin, it is first necessary to blend two or more semi-compatibleolefin polymers by conventional methods, and then prepare an extrudatetherefrom. I have further found that a suitable range. for the blend ofpolyolefins is between 20 and 60 parts by weight of the one polymer,such as polypropylene, and from 80 to 40 parts by weight of anotherpolyolefin, such as linear polyethylene. It is preferred to remainwithin these limits, as tests have shown that when the blend approaches100% by weight of any one of the polymers, the fibrillation of themonofilamcnt becomes quite unsatisfactory and tends toward a cuttingaction, as is desired in preparing staple fibers.

It has been further discovered that a blend of polymers, when extrudedthrough a die having the shape of a trefoil, give the best results inthe subsequent fibrillation of the monofilament produced.

Besides monofilaments composed of blends of the aforementionedhomopolymers of polypropylene and polyethylene, any combination of twoor more polymers comprising, firstly, polypropylene, and secondly, thepolymeric forms of l-butcnc, isobutylene. or a eopolymcr of ethyl cneand l-butcne, may also be used for producing monofilaments that may befibrillated satisfactorily according to this invention. Themonofilaments of the blended polyolefins so produced can then be runover a sharp edge in a variety of ways, such as disclosed in the priorart, and an acceptably fibrillated monofilament will result.

-It is, therefore, an object of this invention to provide an essentiallycontinuous yarn of a polyolefin. It is another object to prepare amultifibrous filament trom a monofilament comprising a blend ofthermoplastic olefin polymers. It is still another object to provide amethod of fibrillating a monofilament of a blend of olefin homopolymers.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention and it should be understood that the latteris not necessarily limited to the aforementioned discussion.

FIGURE 1 is a diagrammatic side elevational view of an apparatussuitable for the practice of this invention;

FIGURE 2 is an elevational view of a die suitable for use according tothis invention; and

FIGURE 3 is an elevational view of a fibrillated monofilament of thisinvention.

The polymers which are used for forming the filamentous articles treatedaccording to my invention are blends of polyolefins of high density,that is, having a density in the range of 0.940 to I00 at 25 C. Thesepolymers include, polypropylene, polyethylene and/or, also copolymers ofethylene with monoole-fins having 3 to 4 carbon atoms per molecule,i.e., propylene, l-butene, or isobutylene. In order for the copolymer tofall in the desired density range the monomer system from which thecopolymer is polymerized should not contain over 30 weight percentpropylene or butene, and preferably not over 15 weight percent based onthe total monomer charge. It is preferred to use in this blend,polyethylene having a density at 25 C. of 0.950 to 0.980 gram per cubiccentimeter.

It should be noted that the blend of polyolefins should comprise firstlypolypropylene and, secondly, a polymer selected from the groupconsisting of polyethylene, polybutene, polyisobutylene, and a copolymerof ethylene and l-butene.

The prefererd method of making a polymer or eopolymer is that describedin the patent to Hogan et al., U.S. 2,825,721. Other methods can beused, for example, low pressure methods employing organometalliccatalysts systems are suitable. An example of such a process is thepolymerization of ethylene in a hydrocarbon diluent in the presence of amixture of triethyl-al-uminum and titanium tetrachloride as the catalystsystem. The temperature can be from room temperature up to about 300 C.with a pressure suflicient to maintain a liquid phase.

Fibers, especially the monofilaments used in my invention, have adiameter of 0.01 to I00 mils and more usually about 0.1 to 50 mils. Thetensile strength of these fibers cold drawn is above 30,000 p.s.i.,frequently above 90,000

to l00,000 p.s.i., and can range as high as 150,000 to 250,000 p.s.i.measured at a temperature in the range of 65 to F.

Reference is now made to the drawing in detail, and to FIGURE 1, inparticular, wherein a molten blend of polymers contained in extruder 5passes through a die 6, which optionally may contain a plurality ofholes of similar cross section. The extruded monofilament 7, only onebeing shown for clarity, passes under a roller 8 in cooling bath 9disposed within the cooling liquid parallel therein. The cooledmonofilament pases from bath 1 1 over and around a pair of Godet rolls12 and 13, from thence it is drawn, preferably at right angles, across asharp cutting edge 14. A strand 16 composed of many fine fibrils passesfrom edge :14 to wind-up roll .17.

In FIGURE 2 is shown a typical ie having an eighthole trefoil crosssection orifice.

in FIGURE 3 is shown a typical multi-fibrous filament which results frompassing the monofilament of a blend of thermoplastic olefin polymers.

Another form of an apparatus which can be conveniently employed inpracticing the method of this invention is that described in the patentto Finlayson et al., U.S. 2,197,857. This apparatus is quite suitablefor the practice of this invention. However, the cutting edge of thepresent invention need not be limited to a razor-like type as disclosedin the referenced patent. Almost any style of sharp cutting edge from arazor-like to a right angle edge will be suitable for fibrillating amonofilament of blended polyolefins. A second feature of the referencedapparatus which can be omitted in the practice of the present invention,is the oscillation of the filament to and fro lengthwise of the cuttingedge. However, this fpature may be employed to prolong the sharpness ofthe cutting edge, and to prevent simultaneous accumulation of loosesevered fragments on the cutting edge.

in density determinations the specimens should be prepared bycompression molding the polymer at 340 F. until completely moltenfollowed by cooling to 200 F. at a rate of about 'F. per minute. Wateris then circulated through the mold jacket to continue the cooling to150 F. at a rate not exceeding F. per minute. The polymer is thenremoved from the mold and cooled to room temperature.

Density was determined by placing a smooth, void-free, pea-sizedspecimen cut from a compression molded slab of the polymer in a 50-ml.,glass-stoppered graduate. Carbon tetrachloride and methyl cyclohexanewere added to the graduate from burettes in proportion such that thespecimen is suspended in the solution. During the addition of theliquids the graduate is shaken to secure thorough mixing. When themixture just suspends the specimen, a portion of the liquid istransferred to a small test tube and placed on the platform of aWestphal balance and the glass bob lowered therein. With the temperatureshown by the thermometer in the bob in the range 73-78-F. the balance isadjusted until the pointer is at zero. The value shown on the scale istaken as the specific gravity. With the balance standardized to read1,000 with a sample of distilled water at 4 C. the specific gravity willbe numerically equal to density in grams per cc.

A better understanding of my invention and appreciation of itsadvantages is provided by the following example.

Thirty parts by weight of a polypropylene resin, in the form of pellets,were admixed with 70 parts by weight of a linear polyethylene, also inthe form of pellets. The two polymers were heated and mixed to assurethorough blending. The molten blend of polymers were then passed to ahopper of a conventional extruding machine,

well known to those skilled in the art. -In this run a 1%" Hartigextruder was employed, using a setting of a screw speed of 2.0. The dieitself was an 8-hole, trefoil orifice. The back pressure was 2,000pounds, and the cylinder temperatures in the three zones, adjacent tothe hopper, intermediate, and next to the die, were 500 F., 500 F., and450 F., respectively. The extruded monofilaments were passed to acooling tank of a conventional type, and then over a pair of Godetrolls. The speed of the first roll was feet per minute, and the secondroll 250 feet per minute. There were produced a number of smooth trefoilmonofilaments. The resulting monofilaments were individually subjectedto mechanical treatment as taught in the apparatus of the Finlaysonpatent. in these runs a sharp metal edge was employed. The blend polymermonofilament separated into many fine fibrils of a desired texture andquality.

Subsequent runs were undertaken in the same equipment employing as thefeed to the extruding equipment either 100% linear polyethylene or 100%polypropylene plastic. Neither of these resulting monofilamentsfibrillatcd as well as the blend polyolefin filament and thereforefailed to produce as satisfactory a type of yarn.

As will be evident to those skilled in the art, various modificationscan be made in my invention without departing from the spirit or scopethereof.

-I claim:

1. A method for fibrillating a monofilament of a blend of at least afirst and second thermoplastic polymer, said first polymer consisting ofpolypropylene, and said second polymer selected from the groupconsisting of polyethylene, polybutene, polyisobutylcnc, and a copolymerof ethylene and l-butene comprising adding said thermoplastic polymcrsto a mixing zone, heating, melting and mixing said polymers therein,extruding as a monofilament the resulting blend of said polymers, saidmonofilament comprising from 20 to 60 parts by weight of said firstpolymer, and to 40 parts by weight of said second polymer, andcontinuously drawing the said monofilament over a sharp edge so thatfibrillation thereof is brought about.

2. In a method for fibrillating a monofilament of a thermoplasticpolymer comprising continuously drawing the monofilament over a sharpedge so that at intervals along the monofilament partial shearingoccurs, the improvement comprising preparing said monofilament from ablend of at last two thermoplastic polymers, the first of which ispolypropylene and the second of which is selected from the groupconsisting of polyethylene, polybutene, polyisobutylene, and a copolymerof ethylene and l-butene said monofilament comprising from 20 to 60parts by weight of said first polymer, and 80 to 40 parts by weight ofsaid second polymer.

3. A method for fibrillating a monofilament of a blend of at least afirst and second thermoplastic polymer, said I first polymer consistingof polypropylene, and said second polymer selected from the groupconsisting of polyethylene, polybutene, polyisobutylene, and a copolymerof ethylene and l-butene comprising adding said thermoplastic polymersto a mixing zone, heating, melting and mixing said polymers therein,extruding as a trefoil cross section monofilament the resulting blend ofsaid polymers, said monofilament comprising from 20 to 60 parts byweight of said first polymer, and 80 to 40 parts by weight of saidsecond polymer, and continuously drawing the said monofilament over asharp edge so that fibrillation thereof is brought about.

4. In a method for fibrillating a monofilament of a thermoplasticpolymer comprising extruding said polymer in the form of a trefoil crosssection monofilament, continuously drawing the monofilment over a sharpedge so that at intervals along the monofilament partial shearingoccurs, the improvement comprising preparing said monofilament from ablend of at least two thermoplastic polymers, sa-id monofilamentcomprising from 20 to 60 parts by weight of said first polymer, and 80to 40 parts by weight of said second polymer, the first of which ispolypropylene and the second of which is selected from the groupconsisting of polyethylene, polybut-ene, polyisobutylene, and acopolymer of ethylene and l-butene.

5. As an article of manufacture, a filbrillated monofilament of ablended thermoplastic material comprising: a first polymer consisting ofpolypropylene and a second polymer selected from the group consisting ofpolyethylene, polybutene, polyisobutylene, and a copolymer of ethyleneand l-butene said monofilament comprising from 20 to 60 parts by weightof said first polymer, and 80 to 40 parts by weight of said secondpolymer.

References Cited in the file of this patent UNITED STATES PATENTS2,531,234 Seckel Nov. 21, 1950 2,700,657 Look et al Jan. 25, 19552,920,349 White Jan. 12. 1960

1. A METHOD FOR FIBRILLATING A MONOFILAMENT OF A BLEND OF AT LEAST AFIRST AND SECOND THERMOPLASTIC POLYMER, SAID FIRST POLYMER CONSISTING OFPOLYPROPYLENE, AND SAID SECOND POLYMER SELECTED FROM THE GROUPCONSISTING OF POLYETHYLENE, POLYBUENE, POLYISOBUTYLENE, AND A COPOLYMEROF ETHYLENE AND 1-BUTENE COMPRISING ADDING SAID THEMOPLASTIC POLYMERS TOA MIXING ZONE, HEATING, MELTING AND MIXING SAID POLYMERS THEREIN,EXTRUDING AS A MONOFILAMENT THE RESULTING BLEND OF SAID POLYMERS, SAIDMONOFILA-